Question

Find out arithmetical mean and standard deviation from this table :
70
60
50
40
Marks obtained
30
20
7
18
Number of students
40
40
63
65
(Ans. SD = 14-02, CSD = 0-39, X = 35-88 )​

Answer 1

Answer:

arithmetic mean = Sum by count

so

now add the the numbers and divide it by the count now you should do it